1. Field of the Invention
The present invention relates to devices for displaying images, and more particularly, to a backlight assembly for providing light in an image display device and a liquid crystal display device having the backlight assembly.
2. Description of the Related Art
In general, liquid crystal display devices displaying images using optical characteristics of liquid crystal have a display panel to display images and a backlight assembly to provide light to the display panel. Backlight assemblies may be classified into edge-type backlight assemblies and direct-downward-type backlight assemblies in terms of the position of lamps generating the light.
In an edge-type backlight assembly, a lamp is disposed at the side of a light guide plate of the backlight assembly. The edge-type backlight assemblies are mainly used for display devices with a small size and/or light weight.
In contrast, multiple lamps are disposed under the display panel in a direct-downward-type backlight assembly. The direct-downward-type backlight assemblies provide light having higher luminance than that of the edge-type backlight assemblies. The direct-downward-type backlight assemblies are mainly used for mid- or large-size display devices.
In the direct-downward-type backlight assemblies, multiple lamps are arranged parallel with each other to generate high luminance light. The lamps in a direct-downward-type backlight assembly are generally external electrode fluorescent lamps (EEFLs), which are readily driven in parallel and cost effective. The lamps (EEFLs) are combined with a lamp socket and received in a mold frame. The lamp socket has multiple clips to secure the lamps and is made of metal to provide electric power to the lamps. The mold frame receiving the lamps is made of synthetic resin.
Since a direct-downward-type backlight assembly employs multiple lamps, the heat generated by the lamps in the direct-downward-type backlight assembly is higher than that in an edge-type backlight assembly. For this reason, the temperature changes inside a direct-downward-type backlight assembly are larger than those in an edge-type backlight assembly.
The lamp socket and the mold frame are generally made of metal and resin, respectively, which have different thermal expansion coefficients. The thermal expansion coefficient of resin is higher than that of metal. Thus, as temperature increases, the volume increase of the mold frame is larger than that of the lamp socket. As a result, the lamp socket is distorted or buckled because of the difference in the volume increases between the mold frame and the lamp socket.
Therefore, a need exists for a backlight assembly which provides high luminance light without such distortion or buckling of the lamp socket. Further, it will be advantageous to provide an image display device employing such a backlight assembly.